Talk:Prenatal hormones and sexual orientation

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[edit] Re-organising information

It seems that the content was moved from homosexuality and has ended up here, in a somewhat incoherent form. As I often do, I started editing this page to fix sloppy writing, find references etc, and ended up seeing deeper problems. It's an interesting topic and deserves to be treated properly.

Firstly, is 'fetal hormones and sexual orientation' the best title for this article? The fetal stage covers the period from the end of the 8th week to birth. But sex differentiation is already occurring at the zygote and embyonic stage. So perhaps 'Prenatal hormones and sexual orientation' is better? (I'm no biologist).

I'd be happy with "prenatal" as a broader description. I think the existing hypotheses really are fetal (or at least that's how they get reported), but that's a good generalization. We should have a redirect if we rename though. Lulu of the Lotus-Eaters 07:07, 2005 August 31 (UTC)

Secondly, the article has a lot of content not directly related to hormones — it's making a more general argument about a biological basis for sexual orientation. It explores links between gender and sexual orientation, and refers to studies that imply a genetic rather than hormonal cause. So I propose either this content is moved elsewhere (more than half of the article) or the broader scope of the article is indicated in its title and introduction (eg Biological basis for sexual orientation). Any thoughts?

Hmmm... that's probably better. It could have subcategories. But there's already a rather mediocre page at Biology_and_sexual_orientation, and it contains some overlapping material with this. I think the best approach might be to snip the good parts from Biology_and_sexual_orientation, and move them into Prenatal hormones and sexual orientation (either cutting with a "see also" back to here, or copying with some duplication). Lulu of the Lotus-Eaters 07:07, 2005 August 31 (UTC)

Thirdly, does anyone have a reference for the Reiner study? I found a similar study of his on the web but the conclusions are quite different to what is presented here. — ntennis 06:07, 31 August 2005 (UTC)

I dunno, there's an anon editor who was pushing this fetal hormone stuff on the Talk:Homosexuality page, and my first draft was just a copy of what he proposed (maybe slight cleanup). You could see if that IP address can be reached: User:70.57.82.114. I was hoping that after I created the page s/he would hop in here to improve it. Lulu of the Lotus-Eaters 07:07, 2005 August 31 (UTC)

There is already a page for the broader argument: Biology and sexual orientation. I propose that all non-hormone related stuff here is merged there. ntennis 06:19, 31 August 2005 (UTC)

Here is the Reiner study from the Boston Globe article:

Males and females have a fundamental genetic difference - females have two X chromosomes, and males have an X and a Y. Still, right after conception, it's hard to tell male and female zygotes apart, except for that tucked-away chromosomal difference. Normally, the changes take shape at a key point of fetal development, when the male brain is masculinized by sex hormones. The female brain is the default. The brain will stay on the female path as long as it is protected from exposure to hormones. The hormonal theory of homosexuality holds that, just as exposure to circulating sex hormones determines whether a fetus will be male or female, such exposure must also influence sexual orientation.
The cases of children born with disorders of "sexual differentiation" offer insight. William Reiner, a psychiatrist and urologist with the University of Oklahoma, has evaluated more than a hundred of these cases. For decades, the standard medical response to boys born with severely inadequate penises (or none at all) was to castrate the boy and have his parents raise him as a girl. But Reiner has found that nurture - even when it involves surgery soon after birth - cannot trump nature. Of the boys with inadequate penises who were raised as girls, he says, "I haven't found one who is sexually attracted to males." The majority of them have transitioned back to being males and report being attracted to females.
During fetal development, sexual identity is set before the sexual organs are formed, Reiner says. Perhaps it's the same for sexual orientation. In his research, of all the babies with X and Y chromosomes who were raised as girls, the only ones he has found who report having female identities and being attracted to males are those who did not have "receptors" to let the male sex hormones do their masculinizing in the womb.
What does this all mean? "Exposure to male hormones in utero dramatically raises the chances of being sexually attracted to females," Reiner says. "We can infer that the absence of male hormone exposure may have something to do with attraction to males."

71.32.199.15 05:33, 7 September 2005 (UTC)

Good for Reiner...of course, the rest of us know that we can NOT infer this; we can only hypothesize this, and then try to design and implement experiments to test the hypothesis.

[edit] Comment from Homosexuality (workspace)

Note: Just putting this here for safe keeping. The tone is way too informal for the article itself, but I'd like to work something in about degrees of correlation suggested. Lulu of the Lotus-Eaters

Actually, my citation can be the very same 2000 Breedlove study that our friend in Farmington includes in Fetal hormones and sexual orientation. Background is that length of ring finger relative to index finger is strongly correlated with fetal testosterone levels. That fact is rather well established quite apart from sexual orientation. Breedlove found an additional much weaker correlation between implied fetal testosterone and sexual orientation, with lesbians in particularly being most strongly androgynized. It's definitely interesting. Gay men show the same pattern (gays more androgynized), but to a smaller degree.

No gay men were shown to be more ANDROGENized androgens are male hormones such as testosterone

However, there is a huge overlap between the suggested fetal testosterone levels and sexual orientation. That is, on average of a bunch of lesbians had higher fetal testosterone than a paired group of straight women. But many lesbians had lower fetal testosterone than the straight-woman average. And many straight women had higher fetal testosterone than the lesbian average. The standard deviation within each group is much more than the mean difference between the groups.

So what does it show? Well, I dunno. There's something potentially interesting there, especially if it can be replicated in much larger samples. But it's hardly clear causation, nor even clear correlation. What it amounts to might be something like (purely hypothetically): "High testesterone exposure female fetuses have a 10% chance of becoming lesbian; low testosterone exposure female fetuses have a 5% chance of becoming lesbian." But that's about the strongest conclusion I can imagine coming out of this (and it hasn't yet, it's been suggested), and that's a relatively weak factor. Lulu of the Lotus-Eaters 23:00, 2005 August 21 (UTC)

There are a quite a few studies looking at digit ratio and sexual orientation. Five of the best are compared by Dennis Mcfadden (in McFadden et el. 2005. A Reanalysis of Five Studies on Sexual Orientation and the Relative Length of the 2nd and 4th Fingers (the 2D:4D Ratio). Archives of Sexual Behavior 34, 341--356.). Another study finds a difference in digit ratio between identical twins that are discordant for sexual orientation (Hall & Love, 2003. Finger-length ratios in female monozygotic twins discordant for sexual orientation. Archives Sexual Behavior 32, 23-28. Pete.Hurd 06:15, 10 September 2005 (UTC)
Hmmm... there must be a pretty darn small sample size of female monozygotes who are discordant on sexual orientation (and who can be located, and are willing to participate in a study). Oddly, I happen to know such a pair; and they happen to be the daughters of a famous researcher on genetic/behavioral causation (of schizophrenia, not of sexual orientation).
Since I don't have easy access to McFadden's survey, can you say what it says? Are effects consistent in direction, as surveyed? What is the relative size of the effect versus the size of the statndard deviations within each sexual orientation, in the aggregate? Etc. Lulu of the Lotus-Eaters 04:17, 19 September 2005 (UTC)

[edit] 1993 Fraternal birth order reference?

The article mentions a 1993 study demonstrating a fraternal birth order effect. This should be provided (and added to the fraternal birth order page). Pete.Hurd 03:58, 19 September 2005 (UTC)

[edit] Fraternal birth order effect not hormonal

As I understand it, the fraternal birth order effect is not thought to be directly hormonal. I can understand that the topic is so closely related to prenatal hormones and sexual orientation that it might belong here, but it makes me wonder why this page isn't part of Biology_and_sexual_orientation. This page really needs a lot of work (but so does the material covering this topic on Biology_and_sexual_orientation page. Pete.Hurd 04:12, 19 September 2005 (UTC)

My feeling is still that this topic is distinct enough that a separate article is warranted, but with appropriately prominent links in both directions to/from Biology and sexual orientation. Then again, I'm a big fan of relatively small self-contained articles over really long, multi-sectioned and exhaustive treatments of all related facets. Lulu of the Lotus-Eaters 04:35, 19 September 2005 (UTC)
Makes sense, the long articles are hard to read. In a perfect workd I think this one would be called uterine effects on sexual orientation, but the present one might make more sense. Pete.Hurd 05:06, 19 September 2005 (UTC)

[edit] The Genetic Component

It is critical to note that these studies still require that homosexuals show a significant heritable component and that this evidence is scarce and difficult to obtain.

Specifically, the production prental hormones is genetically controlled.

Despite this, there is certainly not a preponderance of reliable, statistically significant, and reproducible scientific evidence to support this theory. At best, there is only enough evidence to suggest that further work is necessary.

There is no reason why the hypothesis of prenatal hormones affecting/determining sexual orientation would require any heritable component of sexual orientation. The former hypothesis does not rule out the latter, but they are quite independent. Yes, I can see that a genetic effect on uterine hormone production could be heritable; but it being so is not a logical necessity, just another potentially testable hypothesis. Lulu of the Lotus-Eaters 14:52, 29 October 2005 (UTC)

[edit] East German research

About a year or two before the Berlin Wall came down (1987-1988), I recall seeing a brief report on the television network news about work done by an East German doctor, using rats. He had been intrigued by the spike in homosexuality among boys born in Germany during World War II, and to test his theory, subjected pregnant rats to stresses, such as keeping them in claustrophobic conditions and forcing them to swim until exhaustion. His studies supported the idea of hormonal imbalances caused by stress in mothers contributing to homosexual tendencies in their offspring. A recent Google search turned up nothing. Does any Wikipedian have a clue where to find information on these studies? I think it would be worthwhile to include it in this article. --QuicksilverT @ 00:19, 1 December 2005 (UTC)

I don't know anything about these East German studies, but prenatal maternal stress effects on sexual orientation in rats and makes me think of Ingeborg Ward.
  • Ward, I. (1972) Prenatal stress feminizes and demasculinizes the behavior of males. "Science" 175:82-84
  • Ward et al (2002) Hormonal Mechanisms Underlying Aberrant Sexual Differentiation in Male Rats Prenatally Exposed to Alcohol, Stress, or Both. Archives of Sexual Behavior 31:9-16
  • Ward et al (2003) Fetal testosterone surge: specific modulations induced in male rats by maternal stress and/or alcohol consumption. Hormones and Behavior 43:531-539

I also have a vague tingly feeling that Milton Diamond did some rodent work, (1960's?), but I can't find those references just now. I'm assuming you are aware of Lee Ellis' work, as in

  • Ellis, L. et al (1988) Sexual orientation of human offspring may be altered by severe maternal stress during pregnancy. Journal of Sex Research 25:152--157.
  • Ellis, L. & Cole-Harding, S. (2001) The effects of prenatal stress, and of prenatal alcohol and nicotine exposure, on human sexual orientation. Physiol. Behav. 74:213--226

The thing with rodents, is that while various things may influence sexual behaviour, it is kind of hard to equate it with sexual orientation without waving the hands a bit... Cheers, Pete.Hurd 07:12, 1 December 2005 (UTC)

[edit] Paul Ewald and "gay virus"

Is Ewald's hypothesis that a virus causes homosexuality in all the species (or even, say, just all the mammals) which exhibit homosexuality, or only in humans? Lulu of the Lotus-Eaters 18:33, 23 December 2005 (UTC)

[edit] Section moved over from Biology and sexual orientation

I'm rewriting the section pertaining to prenatal hormones in summary style. The following info was in the section before I hacked away at it, so it could be useful here:

Some have theorized that events in the womb may contribute to some subset of homosexual behavior (though certain individuals may be genetically predisposed to be vulnerable to such events, and the conditions inside the mother's reproductive system are of course influenced by her genetics).
A current hypothesis in this vein is that the developing brains of homosexual men are not as masculinized- or defeminized- as heterosexual men, and that homosexual females are "masculinized" in some way.
Supporting evidence for this hypothesis includes:
  • Observed differences in three areas of the brain in homosexual vs. heterosexual men (the anterior commisure, the supra-chiasmatic nucleus and the interstitial nuclei of the anterior hypothalamus, showing sexual diphormism, although their relation with homosexuality is not clear yet).[1]
  • Observed differences in cognitive testing showing results for homosexual men typical of heterosexual women and results for homosexual women typical of heterosexual men.
  • Observed differences in the preferences that homosexual men, heterosexual men, and heterosexual women have for the age of their sexual partners.
It is unclear whether the observed anatomical and cognitive differences are signs of a (possibly genetic) mechanism that determines sexual orientation, or symptoms of the formation of an atypical sexual orientation during childhood.
One possible mechanism is differential fetal hormone exposure, especially to testosterone (and a compound it is transformed into, estradiol) and luteinizing hormone (LH) is proposed as the mechanism. The concentrations of these chemicals is thought to be influenced by fetal and maternal immune systems, maternal consumption of certain drugs, maternal stress, and direct injection.
Hormone levels may of course vary over time. Given the semi-sequential nature of fetal development, and because multiple hormones are involved, it is possible for the hypothesized "masculinization" or "feminization" process to affect only some body or brain systems. (This is necessary to explain why someone might be say, born with a male body but with a "feminized" sexual attraction.)
Prenatal hormones have been indicated both in Simon LeVay's study of the anterior hypothalamus in cadavers with homosexual contraction of AIDS as cause of death and Marc Breedlove's study of birth order and ring-finger length ratios in living individuals. LeVay's study suggests that homosexual men are "feminized", Breedlove's study suggests that both heterosexual men and homosexual women are "masculinized". Breedlove's study also suggests that homosexual men are "super-males", as their ring-finger lengths were the longest among the four sexual orientations studied.
Researchers at the University of Texas at Austin, lead by Dennis McFadden, found the response of the inner ear to soft sounds tended to be weaker in homosexual women than in heterosexual women. The response among men tended to be weaker than either female group. Fetal exposure to androgens is hypothesized to affect this attribute, suggesting that fetal exposure to the same chemicals may also predispose a daughter to a lesbian orientation. However, lifestyle differences between the two female groups may lead to different sound exposures, and this could also explain the correlation.
References
  • [2]
  • [3]
  • D. McFadden and E. G. Pasanen. Comparison of the auditory systems of heterosexuals and homosexuals: Click-evoked otoacoustic emissions. PNAS, March 3, 1998; 95(5): 2709 - 2713. [4]
Researchers in the Breedlove study found evidence correlating prenatal hormones to male homosexuality. Males exposed to high levels of androgens (sexual hormones) as fetuses are predominantly homosexual.
Certain observations involving "environmental" factors in the womb have been proposed to explain some instances of homosexual orientation; see Genetics and sexual orientation, prenatal hormones and sexual orientation and fraternal birth order for explanations.

Cheers, --Rkitko (talk) 18:39, 18 March 2007 (UTC)

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